新型双向串联型Z源NPC三电平逆变器

传统Z源逆变器启动冲击电流大、不具备能量双向流动能力、存在非正常运行状态、输出电压电平数少。针对上述问题，提出双向串联型Z源NPC三电平逆变器。将串联型Z源网络与NPC三电平逆变器结合，内在抑制启动冲击电流；在阻碍能量回馈的二极管反并联全控开关管，流过全控开关管的电流能够反向流动，进而维持直流链峰值电压稳定，消除非正常运行状态。仿真结果表明：配合软启动策略，改进型拓扑能实现无冲击启动；具备能量双向流动能力；低功率因数时，正常运行；输出线电压电平数增加为5。

Novel Bi-directional Tandem-type Z-source NPC Three-level Inverter

The traditional Z-source inverter has disadvantages such as large start-up inrush current, incapable of bi-directional power flow, existence of abnormal operation state, and small number of output voltage levels. To solve the above problems, a bi-directional tandem-type Z-source NPC three-level inverter is proposed. With the combination of the tandem-type Z-source network and the NPC three-level inverter, the improved topology can inhibit the start-up inrush current. In addition, the diodes that hinder the energy feedback are connected with anti-parallel fully-controlled switch tubes, through which the current can flow reversely. As a result, the DC link peak voltage is kept stable and the abnormal operation state is eliminated. Simulation results indicate that through cooperation with the soft start strategy, the improved topology has no start-up inrush current and possess the capacity of bi-directional power flow. Moreover, the abnormal state is eliminated during the operation at a low power factor, and the number of output line voltage levels increases to 5.